A solid-state image pickup element such as a CCD (Charge-coupled device) and CMOS (Complementary metal-oxide semiconductor) imager, comes to be built in a mobile phone as well as in a video camera and a digital camera, and it is widely used as an inexpensive and low-power-consumption image sensing device.
However, a sensing ability of the solid-state image pickup element is considerably inferior to that of a human being. A contrast between a bright part and a dark part can be sufficiently detected by a human visual sense even when there is a four to five-digit luminance distribution in one visual field. This excellent contrast sensing ability is implemented by a function in which a light receiving cell in the retina can adjust its light sensing characteristics with respect to each cell.
Meanwhile, it is difficult for a conventional solid-state image pickup element to obtain sufficient contrast between a bright part and a dark part in a visual field where there is a considerable difference in brightness in the visual field when an image is picked up at certain timing. That is, when the image is picked up based on one of the bright part and the dark part, brightness of the opposite part is difficult to keep sufficient contrast.
Therefore, Japanese Patent Laying-Open No. 2000-340779 (patent document 1) discloses a semiconductor image pickup element in which a dynamic range is expanded by providing a mechanism capable of shifting a light sensitivity range in each pixel circuit, based on an incident light quantity to peripheral pixels.
In addition, Japanese Patent Laying-Open No. 2004-159274 (patent document 2) discloses a configuration to expand a dynamic range by extracting a low illuminance signal based on long-time accumulation and a high illuminance signal based on short-time accumulation from a pixel circuit to prevent light charges from being saturated in high illuminance, while keeping a configuration of the pixel circuit simple. Similarly, Japanese Patent Laying-Open No. 2004-363666 (patent document 3) discloses that a wide dynamic range imaging condition is dynamically revised to execute adaptive control of a dynamic range by independently extracting a low illuminance signal based on long-time light charge accumulation, a medium illuminance signal based on short-time light charge accumulation, and a high illuminance signal based on ultra-short-time light charge accumulation, and combining those signals through a signal process in a subsequent stage.